ASP.NET Core 2.0 Razor vs Angular/React/etc

My team and I have received funding to start developing an Enterprise level web application (won't go into details of what it does). The application will have many separate web pages but two of those pages being more focused and very heavy - heavy as in a lot of user interaction, modals that display mass data, websocket connections, chat, etc.

I have been assigned to Chief Architect on the project, so I am doing some research into the latest web frameworks. For the back end, we have done some testing and have decided to go with the Azure SQL platform. So far, I am liking the improvements that have been made, and are being made, to ASP.NET with Core 2.0. Specifically the Razor engine, over previous versions of ASP.NET MVC.

I wanted to get some expert opinions on the "new" Razor vs. Angular/React and the like. I'm particularly more concerned with performance. How does Core 2.0 Razor hold up to client side rendering frameworks? Are the differences negligible? Our app is targeting a potential 1,000,000 users (roughly 100,000 concurrent).